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Bird Migration and Air Currents

Subjects

Abstract

AT the annual conference of the International Faculty of Sciences, held in London on January 29-30, Capt. B. Acworth presented a paper entitled “New Light on Bird Migration”. But the paper contains nothing of importance that was not set down lucidly and with similar diagrams in his “This Bondage” in 1929. There is the same useful insistence upon the effects of wind currents upon the movements of birds, and alas, the same errors are repeated. For example, Capt. Acworth insists that the permanent winds of the tropics form impassable barriers; that consequently “the species of birds found in particular temperate zones must have had separate origins”; and that these facts “seem to demolish... the theory of evolution as it affects the common origin’ of birds.” But surely the fact that every autumn and spring in the Old World and the New birds do actually cross, as a matter of routine, the “impassible barrier” of the equatorial currents demolishes the whole argument. Again, the exact knowledge of the writer of the Book of Exodus in describing how “the east wind brought the locusts” is contrasted with the ignorance of biologists, anatomists and embryologists; but records of insect migrations show that the wind is not the directive factor in a large percentage of cases. Lastly, “seasonal winds have always ensured the translation of birds to parts of the world agreeable to the essential needs of the appropriate species”, which, if it means anything at all, means that wind and no biological factor has settled the agreement between birds and their environment.

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